This invention relates to sensors used in flight vehicles, and, more particularly, to a pointing mechanism for sensors used with conformal windows.
Optical sensors are used in aircraft and missile applications to receive radiated energy from a scene and convert it to an electrical signal. The electrical signal is provided to a display or further processed for pattern recognition or the like. The optical sensor and its related optical train, termed a sensor system, are usually packaged in an elongated housing. The sensor may be pivotably mounted within the airframe to allow the optical sensor to be pointed toward subjects of interest.
The sensor system is rather fragile and is easily damaged by dirt, erosion, chemicals, or high air velocity. The sensor system is therefore placed behind a window through which the sensor views the scene and which protects the sensor system from such external agents. The window must be transparent to the radiation of the operating wavelength of the sensor, resist attack from the external forces, and minimally distort the image received by the sensor. The window must also permit the sensor to view the scene over the specified field of regard, which is the specified angular extent over which the sensor must be able to view the scene.
For many applications such as low-speed aircraft and helicopters, the window may be spherical in shape, with the sensor pivot point placed at the center of the sphere to minimize line-of-sight-dependent distortion of the image. However, in higher speed aircraft and missiles the spherical window is unsatisfactory, as it induces a great deal of aerodynamic drag that reduces the maximum speed and range of the vehicle. An elongated, relatively narrow window, termed a conformal window, is therefore preferred for use in high-speed applications to reduce the aerodynamic drag.
The elongated telescope of the sensor system may easily fit within the elongated conformal window when the line of sight of the sensor system lies parallel or nearly parallel to the direction of elongation of the conformal window. If the telescope is pivoted so that the line of sight points at a greater angle to the direction of elongation of the conformal window, the telescope of the sensor system may contact against the inside surface of the window and prevent further movement. One design approach to increasing the allowable pointing angle is to make the elongated telescope of the sensor system and its optics smaller in diameter, but this design variation reduces the aperture size and thence the energy-gathering capability of the sensor system.
There is a need for an improved approach to sensor systems used with conformal windows, which allows the sensor system to be pointed to large line-of-sight pointing angles within the spatial envelope of a conformal window. The present invention fulfills this need, and further provides related advantages.